JPH07233753A - Misfire diagnosing device for multi-cylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To accurately diagnose a misfire on the basis of the cycle of the reference signal from a crank angle sensor without receiving the influence of unevenness of combustion between cylinders. CONSTITUTION:At the time of measuring a period of the reference signal (B) and judging a misfire on the basis of this measurement (C), a period of the reference signal is corrected on the basis of a correction coefficient per each cylinder in each area of the engine operating condition (G). At this stage, a correction coefficient per each cylinder is set on the basis of a ratio, which is obtained by computing a mean value of the period of the reference signal of all cylinders (D) and computing a ratio of each cylinder with the reference signal (E), and the correction coefficient is stored per each area of the engine operation condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire diagnostic device for a multi-cylinder internal combustion engine.

[0002]

2. Description of the Related Art As a conventional misfire diagnostic apparatus for a multi-cylinder internal combustion engine, a crank angle sensor detects a crank angle of 720 ° / n (n
For each cylinder) and continuously measure the cycle of the reference signal corresponding to the combustion state of each cylinder, and determine the presence or absence of misfire according to these fluctuation states based on the cycle of the continuously measured reference signal. There are some that have been decided (actual Kaihei 5-171
72 specification).

[0003]

However, when the misfire diagnosis is performed according to the fluctuation state of the cycle of the reference signal, the cycle of the reference signal corresponding to the combustion state of each cylinder is as follows.
Even if the engine operating condition is constant, it is affected not only by the presence or absence of misfire but also by the combustion variation between cylinders, so there is a problem that accurate misfire diagnosis cannot be performed unless this effect is removed. .

In view of such conventional problems, an object of the present invention is to improve the accuracy of misfire diagnosis by learning the combustion variation between cylinders for each region of engine operating state.

[0005]

For this reason, the present invention is constructed as shown in FIG. That is, the crank angle is 720 °
/ N (n is the number of cylinders), a reference signal generating means A for generating a reference signal including a cylinder discrimination signal, and a cycle measuring means B for measuring the cycle of the reference signal corresponding to the combustion state of each cylinder. And a misfire determination means C for determining whether or not there is a misfire in each cylinder based on the cycle of the reference signal.

Then, the cycle average value calculating means D for calculating the average value of the cycle of the reference signals of all the cylinders while the misfire judging means C judges that there is no misfire, and the cycle of the reference signal of each cylinder and the above Ratio calculating means E for calculating the ratio with the average value
And a correction coefficient storage means F for storing the correction coefficient for each cylinder set based on the ratio for each region of the engine operating state.

Then, between the cycle measuring means B and the misfire determining means C, the cycle of the reference signal of each cylinder obtained by the cycle measuring means B is stored in the storage means F for each region of the engine operating state. The misfire determination means C is corrected on the basis of the corrected cycle.
A cycle correction means G is provided for making the determination by. Here, the storage means F sets a new correction coefficient based on the correction coefficient for each cylinder already stored for each region of the engine operating state and the ratio calculated by the ratio calculation means E, It is preferable to have a correction coefficient updating means f for updating the stored value.

Further, the cycle correction means G is arranged so that when the storage means F does not store the correction coefficient for each cylinder corresponding to the region of the current engine operating state, the engine speed in the engine operating state is It is preferable to have a correction coefficient estimating means g for estimating the correction coefficient from the correction coefficient for each cylinder stored corresponding to another equal area.

[0009]

In the above structure, prior to the misfire determination,
By correcting the cycle of the reference signal measured as corresponding to the combustion state of each cylinder by the correction coefficient for each cylinder in each region of the engine operating state, it is possible to avoid the combustion variation between the cylinders. Therefore, the average value of the cycles of the reference signals of all the cylinders during the period when it is determined that there is no misfire is calculated, and the ratio between the cycle of the reference signals of each cylinder and the average value is calculated.
Then, a correction coefficient is set for each cylinder based on the ratio and stored for each region of the engine operating state. By using such a correction coefficient for each cylinder and region of engine operating state,
It is possible to avoid variations in combustion between cylinders.

When setting and storing the correction coefficient,
By setting a new correction coefficient based on the correction coefficient already stored and the ratio, and updating the stored value,
The reliability of learning can be improved. Further, until the learning for each region of the engine operating state is completed, by estimating by referring to the correction coefficient stored corresponding to another region of the engine operating state where the engine speed is equal, The correction can be started immediately.

[0011]

EXAMPLE An example of the present invention will be described below. 4
In a cylinder internal combustion engine, the ignition sequence is # 1 → # 3 → # 4 → # 2
And FIG. 2 shows the system configuration. The control unit 10 has a built-in microcomputer, performs arithmetic processing based on signals from various sensors, and has a fuel injection valve 2 provided for each cylinder (# 1 to # 4) of the engine 1.
And controlling the operation of the ignition coil 3.

A crank angle sensor 11, an air flow meter 12, an idle switch 13 and the like are provided as the various sensors. Crank angle sensor 11
By outputting a reference signal for each 180 ° and a unit signal for each unit crank angle (1 to 2 °), the crank angle can be detected and the engine speed N can be detected. Further, the reference signal includes a cylinder discrimination signal. For example, by increasing the pulse width of the reference signal corresponding to the # 1 cylinder,
Cylinder discrimination is possible. The crank angle sensor constitutes a reference signal generating means.

The air flow meter 12 is, for example, a hot wire type,
The intake air flow rate Q can be detected. Idle switch 13
Is turned on by detecting the fully closed position of the throttle valve. Here, the control unit 10 determines the basic fuel injection amount Tp = K based on the intake air flow rate Q and the engine speed N.
・ Q / N (K is a constant) is calculated, and various corrections are applied to this to obtain the final fuel injection amount Ti = Tp · COEF (COFF
Various correction coefficients), and a drive pulse signal having a pulse width corresponding to Ti is output to the fuel injection valve 2 of each cylinder at a predetermined timing synchronized with the engine rotation to perform fuel injection. However, when decelerating, the idle switch 13 is ON,
Moreover, when the engine speed N is equal to or higher than a predetermined fuel cut speed, the output of the drive pulse signal to the fuel injection valve 2 is stopped and the fuel cut is performed. This fuel cut is canceled when the engine speed N becomes lower than a predetermined recovery speed or the idle switch 13 is turned off.

The control unit 10 also determines the ignition timing based on the engine speed N and the basic fuel injection amount Tp, and controls the operation of the ignition coil 3 at that timing.
Ignite. Further, the control unit 10 determines whether or not there is a misfire in each cylinder in accordance with the misfire diagnosis routine shown in FIGS. 3 to 4, and issues a warning by a warning lamp or the like in a predetermined case.

Regarding the misfire diagnosis routine shown in FIGS. 3 to 4,
This will be described with reference to FIG. This routine is executed in synchronization with the generation of the reference signal from the crank angle sensor. In step 1 (denoted as S1 in the figure. The same applies hereinafter), in the case of four cylinders, the latest value of the cycle of the reference signal is set to 5
Since individual pieces (T1 to T5) are stored and the misfire determination is performed based on these, the cycle used last time is replaced as follows.

T5 ← T4, T4 ← T3, T3 ← T2, T2 ← T1 In addition, the measured value of the timer is read and set as T1 (T
1 ← timer). This timer was started at 0 in the previous routine, and the cycle of the latest reference signal is measured as T1. Therefore, this portion corresponds to the period measuring means. In step 2, the timer is reset to start 0 for the next measurement.

In step 3, the cylinder is discriminated, that is, the cylinder in which combustion is almost completed at present is discriminated. Here, the cylinder for which the cylinder is determined is i. As a result, the misfire determination cylinder this time becomes the cylinder i, and the cycle of the reference signal corresponding to the combustion state of the cylinder i is measured as T1.
Since the ignition order is # 1 → # 3 → # 4 → # 2,
In the ignition order, if the cylinder one cylinder before i is i-1, the cylinder two cylinders before is i-2, and the cylinder three cylinders before is i-3, the correspondence is as shown in the table below.

[0018]

[Table 1]

At step 4, it is judged whether or not the learning condition is satisfied. Here, the learning condition means that there is no misfire during the previous four cycles T2 to T5, and that the engine speed N and the basic fuel injection amount (load) are parameters of the engine operating state. ) There is no extreme fluctuation of Tp. Steps 5 to 9 are executed for learning only when the learning condition is satisfied.

In step 5, as the cycle of the reference signal for all cylinders, T _AVE is calculated as an average value of the previous four cycles T2 to T5 according to the following equation. This portion corresponds to the periodic average value calculation means. T _AVE = (T2 + T3 + T4 + T5) / 4 In step 6, the ratio (correction coefficient) KT1 between the cycle (latest cycle) T1 of the reference signal of the cylinder i and the average value T _AVE is calculated according to the following equation. This part corresponds to the ratio calculation means.

KT1 = T1 / T _{AVE In} step 7, the map for cylinder i is selected from the maps provided for each cylinder, and the engine speed N and basic fuel injection amount (load) Tp are selected from the selected map. And the correction coefficient KT _i stored as parameters (the correction coefficient KT corresponding to the current engine speed N and the basic fuel injection amount Tp).
_i ) is read. Before learning, KT _i = 1.

In step 8, a new correction coefficient K is calculated based on the correction coefficient KT _i read in step 7 and the ratio (correction coefficient) KT1 calculated in step 6 according to the following equation.
Set T _i . x is a weighting constant. KT _i = [(x−1) / x] KT _i + (1 / x) KT1 In step 9, the newly set KT _i is set to the current engine speed N and basic fuel injection amount Tp in the map of cylinder i. Write as data corresponding to and to update the stored value.

Therefore, the steps 7 to 9 correspond to the correction coefficient storage means (including the correction coefficient updating means). In step 10, it is determined whether learning has been completed, that is, correction coefficient learning (writing to the map) has been performed a predetermined number of times or more for each cylinder. If learning has been completed, the process proceeds to step 11.

In step 11, it is determined whether or not the region of the current engine operating state (N, Tp) is a learned area. If it is a learned area, the process proceeds to step 12, and if it is an unlearned area, the step is performed. Proceed to 13. In step 12, the correction coefficients KT _{i to} KT _i-3 in the regions corresponding to the current engine speed N and the basic fuel injection amount Tp are retrieved from the maps of the cylinders i to (i-3), respectively, and step 14 Go to.

In step 13, correction coefficients KT _{i to} KT _i-3 in other regions corresponding to the current engine speed N are retrieved from the map of cylinders i to (i-3), and the process proceeds to step 14.
That is, when the correction coefficient is not stored corresponding to the region of the current engine operating state, by using the correction coefficient stored corresponding to the other region of the engine operating state where the engine speed is equal, Estimate the correction factor.

In step 14, the cycle data (T1 to T5) of the reference signal for misfire determination is corrected by the correction coefficient for each cylinder according to the following equation, and the corrected cycle data (HT
1-HT5). HT1 = T1 / KT _i HT2 = T2 / KT _i-1 HT3 = T3 / KT _i-2 HT4 = T4 / KT _i-3 HT5 = T5 / KT _i Therefore, steps 11 to 14 are the period correction means (correction). (Including coefficient estimating means).

In step 15, the misfire determination value M is calculated from the corrected cycle data (HT1 to HT5) according to the following equation.
Calculate ISA. After this, the process proceeds to step 17. MISA = [3 × (HT4-HT5) + (HT4-HT
1)] / HT5 ³ If it is not learned in the determination in step 10, the process proceeds to step 16 and the data of the cycle without correction (T1 to T
From 5), the misfire determination value MISA is calculated according to the following equation. After this, the process proceeds to step 17.

MISA = [3 × (T4−T5) + (T4
In -T1)] / T5 ³ step 17, by referring to a map of the engine speed N and the basic fuel injection quantity Tp as parameters, sets the reference value SL for determining misfire. In step 18, the misfire determination value MI
SA is compared with the reference value SL, and if MISA ≧ SL, the process proceeds to step 19 and it is determined that there is a misfire. Therefore, step 15
The part from 19 corresponds to the misfire determination means.

The misfire determination value is the above-mentioned MISA.
The following MISB can be used instead of MISB = [2 × (HT3-HT5) + 2 × (HT3-
HT1)] / HT5 ³ or, MISB = [2 × (T3-T5) + 2 × (T3-T
1)] / T5 ³ For this MISB, the latest three values (MISB
1 to MISB3) are stored, and as a misfire determination value,
The following MISC may be used.

MISC = MISB2-MISB3 For these misfire determination values, MISB ≧ predetermined value, M
If ISC ≧ predetermined value, it is determined as misfire. Also, when it is determined that there is a misfire, of course, to determine the misfiring cylinder,
An alarm or the like should be issued according to the number of consecutive times.

[0031]

As described above, according to the present invention, it is possible to obtain an accurate misfire diagnosis without being affected by combustion variations among cylinders. Further, when setting and storing the correction coefficient, the reliability of learning can be improved by updating the correction coefficient in consideration of the already stored correction coefficient.

In addition, until the learning for each region of the engine operating state is completed, by using a method called estimation,
The correction can be started immediately.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart of a misfire diagnosis routine (No. 1).

FIG. 4 is a flowchart (part 2) of a misfire diagnosis routine.

FIG. 5 is a diagram showing how the cycle changes due to variations in combustion.

[Explanation of symbols]

 1 engine 2 fuel injection valve 3 ignition coil 10 control unit 11 crank angle sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02P 17/12 G01M 15/00 Z

Claims (3)

[Claims] 1. A reference signal generating means for generating a reference signal including a cylinder discrimination signal for each crank angle of 720 ° / n (n is the number of cylinders), and a cycle of the reference signal corresponding to a combustion state of each cylinder is measured. In a misfire diagnosing device for a multi-cylinder internal combustion engine, which comprises a cycle measuring means and a misfire determining means for determining whether or not there is misfire in each cylinder based on the cycle of the measured reference signal, the misfire determining means determines that there is no misfire. Period average value calculating means for calculating the average value of the cycle of the reference signals of all cylinders, ratio calculating means for calculating the ratio of the cycle of the reference signal of each cylinder and the average value, based on the ratio While the correction coefficient storage means for storing the correction coefficient for each cylinder set by each region of the engine operating state is provided, the correction coefficient storage means is provided between the cycle measurement means and the misfire determination means. Standard signal for each cylinder The cycle correction means is provided for correcting the cycle of the signal by the correction coefficient for each cylinder stored in the storage means for each region of the engine operating state, and for making the determination by the misfire determination means based on the corrected cycle. A misfire diagnostic device for a multi-cylinder internal combustion engine, which is characterized in that: 2. The storage means sets a new correction coefficient on the basis of the correction coefficient for each cylinder already stored for each region of the engine operating state and the ratio calculated by the ratio calculating means, The misfire diagnosis apparatus for a multi-cylinder internal combustion engine according to claim 1, further comprising a correction coefficient updating means for updating the stored value. 3. The cycle correction means, when the correction coefficient for each cylinder corresponding to the region of the current engine operating state is not stored in the storage means, the engine rotational speed is the same among the engine operating states. 3. The multi-cylinder internal combustion engine according to claim 1 or 2, further comprising a correction coefficient estimating means for estimating the correction coefficient from the correction coefficient for each cylinder stored in correspondence with the region of FIG. Misfire diagnostic device.